JAEA-Review-2010-065.pdf:15.99MB - 日本原子力研究開発機構

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Processing of an Upstanding Nano-Wire Array Using
Ion-Beam Lithography
K. Takano a) , T. Satoh a) , T. Kamiya a) , Y. Ishii a) , T. Ohkubo a) , M. Kohka a) ,
M. Sugimoto b) , S. Seki c) and H. Nishikawa d)
a) Department of Advanced Radiation Technology, TARRI, JAEA, b) Environment and Industrial
Materials Research Division, QuBS, JAEA, c) Graduate School of Engineering, Osaka University,
d) Department of Electrical Engineering, Shibaura Institute of Technology
Recently, heavy ion irradiation for polymer films at the
energy range of hundred MeV has been expected to be a
promising tool for a new micro-processing technique to
fabricate wire structures with the diameter of nano meter
size, nano-wire 1) . The nano-wires are fabricated by the
irradiation to induce the cross-linking reaction of the
polymer within an ion track along the ion trajectory as a
negative photolithography process. At the developing with
an organic solvent after irradiation, the wires are lying down
the substrate, flowing away, or sticking to neighbor wires.
In order to avoid the lying and the flowing, a fabrication of
upstanding nano-wires which are supported by bridge
structure has been tried by ion beam lithography with the
focusing systems of the light and heavy ion beams at the
TIARA.
As the target samples, tri-layer films were fabricated by
stacking of a processing layer, a buffer layer, and a substrate.
The processing layer was a SU-8 negative photoresist gel
which was spin-coated with 20 m thickness. The buffer
layer consists of cured SU-8 negative photoresist by
irradiation of electron beam 0.5 MeV or 60 Co gamma ray at
Takasaki. The substrate was selected clear polyethylene
terephthalate sheets. The irradiation was carried out as
follows; 1) the focused 1 H + beam of 3 MeV, which
penetrated the gel layer, was scanned with bridge pier
pattern, 2) bridging between the piers was performed by
drawing of girder pattern with the focused 1 H + beam of
0.5 MeV, of which the penetration depth of 7 m was
shorter than the gel thickness, 3) matrix writing in air was
performed by the single ion hit of 20 Ne 7+ of 260 MeV with
spot writing at 500 ions/spots, as shown in Fig. 1. After a
post-baking at 95 °C for 20 min, the written films were
developed by a fluidic pumping with propylene glycol
monomethyl ether acetate at the flow rate of 1.4 mL/min for
charge and discharge.
The fabrication of upstanding nano-wires was successful,
not randomly strung but arrayed by the single ion hit
between the bridge girder with long span of 80 m and the
buffer layer, as shown in Fig. 2. The buffer layer promoted
the bond of the wires to the substrate. However, the
neighbor wires gather mutually and sticking. In order to
avoid this sticking problem, the supercritical fluid drying
method with carbon dioxide or other new developing
processes will be tried as the next step.
Reference
1) S. Tsukuda, et al., Appl. Phys. Lett. 87 (2005) 233119.
JAEA-Review 2010-065
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Fig. 1 Scheme of the process for upstanding nano-wire
array which was supported by bridge structure in the
ion beam writing. 1) 3 MeV H + beam writing for
the bridge pier pattern, 2) 0.5 MeV H + beam writing
the bridge girder pattern, and 3) wire string by single
ion hit of 260 MeV 20 Ne 7+ .
Fig. 2 SEM image of the upstanding nano-wire array
which was strung between the bridge girder and the
substrate by single ion hit of 260 MeV 20 Ne 7+ .